Electric storage devices, particularly lithium secondary batteries, become widespread rapidly for small batteries such as portable equipment power supplies, and further the development of large lithium secondary batteries for the electric power industry, automobiles, and the like is also promoted. Long-term reliability and high input and output characteristics are required of electrode active materials used in such electric storage devices, particularly lithium secondary batteries, and safety and life characteristics are required particularly of negative electrode active materials. Therefore, lithium titanate excellent in these characteristics is regarded as promising.
As the above lithium titanate, several compounds are present as described, for example, in Patent Literature 1. Patent Literature 1 describes lithium titanate represented by the general formula LixTiyO4 in which 0.8≤x≤1.4 and 1.6≤y≤2.2 and illustrates LiTi2O4, Li1.33Ti1.66O4, Li0.8Ti2.2O4, and the like as typical examples. As methods for producing such lithium titanate, a wet method in which predetermined amounts of a lithium compound and a titanium compound are mixed in a medium liquid, and the mixture is dried and then fired (Patent Literature 2), and, among the above wet method, a method of performing drying by spray drying (Patent Literature 3) are known. In addition, a dry method in which a titanium oxide having a specific surface area of 50 to 450 m2/g as measured by a BET one-point method by nitrogen adsorption is used as a raw material and mixed with a predetermined amount of a lithium compound, and the mixture is fired (Patent Literature 4), and the like are also known.